I currently have things like resist energy, protection from arrows, protection from evil... are there any other spells and effects I may have forgotten or what do you use when you're up against a super strong caster to protect yourself? New character is going to be level 5, campaign should end around level 12.

Backstory
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The motivation that sparked this was a BBEG in a previous campaign that could use intensified maximized snowball that he could change the element type and hit for.. I think it was about 120 damage. Same story for fireball etc. He also got 2 cast a turn on most turns. We encountered this at level 10 and got absolutely destroyed.

I currently have things like resist energy, protection from arrows, protection from evil... are there any other spells and effects I may have forgotten or what do you use when you're up against a super strong caster to protect yourself? New character is going to be level 5, campaign should end around level 12.

Backstory
---------------
The motivation that sparked this was a BBEG in a previous campaign that could use intensified maximized snowball that he could change the element type and hit for.. I think it was about 120 damage. Same story for fireball etc. He also got 2 cast a turn on most turns. We encountered this at level 10 and got absolutely destroyed.

This seems like itd do what you're looking for while not being ....EXACTLY the same. Under arcanist, the counterspell build

Snowball- Protection from Elements (Cold) will provide immunity to cold at 12/hp level to max of 120 hp. Keep another memorized, perhaps Quickened. to provide continued coverage as the first runs out or low on protection left. Would also help vs Fireball.

Anything that allows SR will be stopped by Spell Immunity or Greater Spell Immunity. Extend metamagic helpful. Everything except Snowball and Black Tentacles on your list would be stopped. Downside is the spell is generally a divine spell so if you are an arcane caster an investment in UMD.

Gaseous Form provides DR=10/magic and makes you insubstantial. Unfortunately "insubstantial" isn't a defined game term so you may or may not be immune to grapple attempts. Ask your GM, YYMV. It also requires an investment in Metamagic to be able to cast spells while Gaseous. I did have a character though that used it to great effect. She would cast Gaseous Form then surround herself with Black Tentacles. Not much could get at her at that point without risking getting grappled trying to reach her.

Dispel Magic will get rid of Summons (and is a universal counterspelling choice AFAIK)

The globe of invulnerability spells are probably exactly what yo are looking for.

Globe of Invulnerability, Lesser
Source PRPG Core Rulebook pg. 290
School abjuration; Level arcanist 4, occultist 4, psychic 4, sorcerer 4, wizard 4
Casting
Casting Time 1 standard action
Components V, S, M (a glass or crystal bead)
Effect
Range 10 ft.
Area 10-ft.-radius spherical emanation, centered on you
Duration 1 round/level (D)
Saving Throw none; Spell Resistance no
Description
An immobile, faintly shimmering magical sphere surrounds you and excludes all spell effects of 3rd level or lower. The area or effect of any such spells does not include the area of the lesser globe of invulnerability. Such spells fail to affect any target located within the globe. Excluded effects include spell-like abilities and spells or spell-like effects from items. Any type of spell, however, can be cast through or out of the magical globe. Spells of 4th level and higher are not affected by the globe, nor are spells already in effect when the globe is cast. The globe can be brought down by a dispel magic spell. You can leave and return to the globe without penalty.

Note that spell effects are not disrupted unless their effects enter the globe, and even then they are merely suppressed, not dispelled.

If a given spell has more than one level depending on which character class is casting it, use the level appropriate to the caster to determine whether lesser globe of invulnerability stops it.